Thanks for stopping by. This is where I publish a lot of my features and thoughts on HF propagation, antennas and other ham radio topics. I write for a number of radio magazines, including the RSGB's RadCom and ARRL's QST. I am also chairman of the RSGB's Propagation Studies Committee. When not playing radio I'm a professional journalist specialising in aerospace, science and technology and author of the RSGB's "Stealth Antennas" and "An Introduction to Antenna Modelling".

Friday, 23 October 2009

Making sense of 10m propagation

What's this? G stations working VK on 10m at sunspot minimum? Jordan and Thailand audible on 10m on a 65ft end fed?

That can't be right!

Well, it looks like it is. So why did 10m suddenly open up this week?

I think we need to look at a number of factors. First the solar flux was 72 so obviously no massive increase in solar UV output has caused it.

But it is October and this is a peak month for DX. The ionosphere in the Northern Hemisphere is cooling down, becoming more dense and the chemical composition changes too in the Winter compared with Summer, giving us a greater ion density.

To quote J K Hargreaves' “The Solar Terrestrial Environment”: You get an increase in NO concentration and a decrease ion loss rate due to the removal of water-cluster ions and a change in chemical reaction rates due to the temperature change.

In fact, if you feeling really awake read the whole 414 pages – I am sure the more I read the less I understand!

Anyway, so is that the whole story? No!

At the time of the openings the he Bz (Interplanetary Magnetic Field) was pointing south which means that solar wind was coupling with the earth's magnetic field and hot ions were pouring in.

Hence the 6m aurora the previous night – see www.solarcycle24.com.

The three-hourly K index reached 4 showing the effects of these ions on the earth's magnetic field.

So what we probably saw was a pre-auroral enhancement and that condx on the upper HF bands while good, are going to get worse. I'll let you know if I was right.

And they say that a high K index is bad for propagation – not always at the outset though.

Earth’s Magnetic Field Is Produced By An External Dynamo System, Not An Internal Dynamo.

Researcher finds that Earth’s magnetic field is not produced by an internal dynamo. Nor is it produced by ocean current. The dynamo is outside the Planet! New findings by independent researcher, Dennis Brooks, show that Earth’s magnetic field and the planet itself are components of a complex dynamo system, which surrounds the planet. The planet and its magnetic field are part of the dynamo.

According to this new theory, no internal dynamo or ocean current helps in producing or maintaining the magnetic field because other planets with magnetic fields do not have ocean currents or iron cores.

Image by NASA

Each planet does not have a unique way of producing its magnetic field. The magnetic field of each planet is produced by a planetary dynamo system and its ring current.

For many years researchers thought that a similar dynamo system was within the planet and that this internal dynamo generated the magnetic field. However, we know now that it is too hot inside the planet to produce and maintain a magnetic field there.

The planetary dynamo system is composed of a magnetosphere, the planet, the magnetic field, radiation belts, ring current, and charged particles from the solar wind. The planet is the central component of the system and its rotation plays an important part in operating the dynamo and generating ring current. The magnetic field is generated by the system’s ring current, which is made up of charged particles. The magnetic field captures even more charged particles and brings them into the dynamo system as fuel. Everything works together.

Earth’s inner and outer core simply cannot provide the fuel a dynamo system needs. If earth’s dynamo had to depend on energy from the planet for fuel, the entire planet would have been completely consumed many years ago.

To learn more about Earth’s magnetic field, Visit http://sites.google.com/site/earthsmagneticfield/

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